3.2.4.3 - Cell Mediated Immunity

Question 1

Which type of immunity are T-lymphocytes mainly involved in?

Answer 1

Cell Mediated Immunity (they are just used to stimulate B-cells in humoural immunity)

Question 2

Where can non-self antigens be found that T-lymphocytes may bind to?

Answer 2

• The surface of an antigen presenting cell (phagocyte)
• Body cells invaded by a virus may present viral antigens.
• Transplanted cells from organ donors.
• Cancer cells
• Toxins produced by pathogens.

Question 3

Can T-lymphocytes bind to non-self antigens floating around freely in the blood?

Answer 3

No - they can only bind to foreign antigens that have been presented on an antigen presenting cell e.g. phagocyte.

Question 4

How do cytotoxic T lymphocytes (T_c) protect against disease?

Answer 4

They kill cells infected by pathogens or cancerous cells.

They produce a protein called perforin.

Perforin creates holes in target cell membranes, which kills the cell.

Question 5

Where do T-lymphocytes mature?

Answer 5

In the thymus

Question 6

Where are all lymphocytes produced?

Answer 6

Bone marrow

Question 7

Where do B-Lymphocytes mature?

Answer 7

In the bone marrow.

Question 8

What is meant by cell mediated immunity?

Answer 8

An immune response that does not involve the production of antibodies.

Results in the production of cytotoxic T cells that can protect against pathogens.

Question 9

Describe the process of cell mediated immunity (immunity that does not result in the production of antibodies).

Answer 9

1. Phagocytosis of foreign material by phagocyte.
2. Foreign antigens from material are presented on phagocyte.
3. Specific T-helper lymphocyte (T_h) binds to foreign antigen (clonal selection)
4. Attachment causes T_h cell to undergo mitosis (clonal expansion).
5. Cloned T cells can:

• become memory cells for rapid future response.to same pathogen.
• stimulate phagocytes to engulf via phagocytosis.
• stimulate B cells to divide and release antibodies (humoural response)
• activate cytotoxic T cells (T_c) cells to kill.

Question 10

What can the cloned T-lymphocytes do after clonal expansion has taken place in the cell mediated response?

Answer 10

• become memory cells for rapid future response.to same pathogen.
• stimulate phagocytes to engulf via phagocytosis.
• stimulate B cells to divide and release antibodies (humoural response)
• activate cytotoxic T cells (Tc) cells to kill.

Question 11

what is an antigen?

Answer 11

foreign protein that can stimulate an immune response/production of antibodies

Question 12

what is an antibody?

Answer 12

Protein specific to an antigen

produced by B cells/secreted by plasma cells